Modern machines for developing photographic films or papers comprise several processing tanks arranged one behind the other. These tanks contain various processing baths through which the photographic paper or film to be developed is passed in succession. For this purpose, the papers or film is carried by holders or processing racks which may be suspended as desired and in any desired combination in the individual baths. A common drive for the holders or racks is provided at the side of each tank and the individual holders or racks are coupled to this drive when they are suspended in a tank, in order to start up the rollers thereof.
The known processing racks have rollers or cylinders for transporting the photographic material to be processed. These are arranged on horizontal axes one above the other. The present invention relates to a holder or rack in which the photographic material to be treated is passed between rollers arranged in a frame. The opposite rollers co-operate to transport and guide the photographic material, so that even relatively short films or strips of paper may be passed through the individual baths without difficulty. In order to achieve this, the co-operating surfaces of the rollers contact each other with a pressure.
In known holders for machines for developing photographs, the co-operating surfaces of the rollers are pressed against each other by one roller of each pair of rollers being adjustably mounted in relation to an opposing and fixed roller and being pressed against this fixed roller by means of springs. The fixed roller has a rigid surface, for example a steel casing, while the opposing roller is a resilient roller such as a rubber roller. An arrangement of this type has the disadvantage that the rollers of each pair of rollers are pressed against each other even when the machine is inoperative, so that pressure points may be produced on the elastic roller in the event of prolonged stationary periods. If photographic material to be developed runs through a pair of rollers of this type, then the adjustable roller lifts off the fixed roller, causing tilting if the photographic material passes between the pair of rollers on one side. Another disadvantage lies in the fact that particles of dirt which are deposited on the surface of one roller may also cause the rollers to move apart and cause scratches on the opposing roller and the passing photographic material. Finally, a uniform pressure between the co-operating rollers of a pair of rollers is only ensured if the rollers are mounted exactly parallel to each other and do not bend or sag.
An object of the present invention is to overcome these disadvantages and to provide a holder for machines for processing photographs in which the surfaces of the rollers contact each other and against the passing photographic material, with a pressure which is regulated automatically even during operation and which is uniform throughout, and which accordingly are not lifted apart when the photographic material or other irregularities pass through.